To describe the invention in greater detail, a number of publications and documents are referenced in the present application. The disclosure of each of these publications and documents is incorporated by reference in its entirety.
In general, the invention relates to methods for treating neurological and psychiatric diseases. Neurological and psychiatric diseases/disorders often progress rapidly and can be disruptive of essentially all aspects of a human or animal patient's life. Thus, these diseases present profound challenges for the patients, care givers, and attending physicians. In addition, the progressive nature of these diseases makes the passage of time a crucial consideration in the treatment process. Treatment of neurological or psychiatric diseases, particularly those affecting cognitive function, can be complicated by the duration of time which is frequently required to determine the efficacy of a therapeutic regimen. Depending on the disease involved, a considerable proportion of affected patients may present with an intractable form of disease.
Methodology directed at human and animal gene therapy renders feasible the treatment of numerous neurological and psychiatric diseases via delivery of a combination of nucleic acid sequences directly to the nervous system, wherein their expression can be manipulated in a therapeutically beneficial manner. This is a particularly valuable option for patients with intractable neurological disease, who may, for example, have a form of the disease that is not responsive to available drugs or may not be able to tolerate the unwanted side effects associated with many therapeutics. However, gene transfer into the central nervous system (CNS) is impeded by several features of the system, including the largely post-mitotic nature of most neurons in the brain, obstacles pertaining to the blood-brain-barrier or constraints related to low accessibility into several brain areas.
Applying retroviral vectors that are routinely used for somatic cell gene transfer is not useful, in general, for applications in post-mitotic neural cells because retrovirally mediated gene transfer requires at least one cell division in target brain cells for integration and expression. To address this challenge of gene transfer into the CNS, a number of vectors and non-viral methods have been developed. A number of studies have achieved varying degrees of success for gene transfer into the CNS using either an ex vivo approach, involving transplantation of cells retrovirally-transduced in vitro, or an in vivo approach. HSV-1 and adenoviral vectors, as well as non-viral methods, including cationic lipid mediated transfection, have also been utilized for gene transfer into neural cells of the CNS.
For instance, oligodendrocytes that were infected ex vivo with retroviral vectors have been transplanted into a syngenic rat model for a demyelinating disorder. Fibro and primary muscle cells have also been used successfully to introduce exogenous nucleic acid sequences and their encoded products into the CNS.
Herpes Simplex Virus (HSV-1) and a number of adenoviral vectors have been used in vivo causing persistent expression (i.e., at least two months) of marker genes in the rat brain. Besides viral vector approaches, some investigators have directly injected a cationic liposome:plasmid complex and have shown low levels and transient expression of a marker gene using this approach.
Nonetheless, relatively few studies have aimed at introducing “therapeutic” genes into cells of the CNS and the majority of these studies employed an ex vivo approach with transduction of fibroblasts and muscle cells with the human tyrosine hydroxylase gene that provided a source of L-dopa-secreting cells in models of Parkinson's disease. In vivo approaches have used HSV vectors to induce expression of beta-glucuronidase, glucose transporter, and nerve growth factor and an adenoviral vector to induce low-level transient expression of human alfa1-antitrypsin.
Few clinical studies documenting gene transfer into the brain have been reported. In one of these, rats were basically cured after intracerebral implantation of glioma cell lines infected with a retrovirus expressing the HSV-1 thymidine kinase gene following subsequent treatment with ganciclovir.
More recently, as described in patent PCT WO 2005/037211 A2, using an AAV vector, injection of the NPY gene into hippocampal formation of the rat caused overexpression of NPY that significantly reduced epileptic activity (Richichi et al. (2004) J. Neurosci. 24:3051-9). Injection of AAV-vectors containing NPY was studied in three rat epilepsy models, (1) intrahippocampal kainate injection, (2) intraventricular kainate, and (3) rapid kindling. Intrahippocampal injection of the NPY-AAV vector in rats caused long-lasting (at least 3 months) expression of NPY and decreased seizure activity in all three models, but, importantly, did not abolish seizure activity.
Also using AAV vectors, induced expression of galanin, another inhibitory neuropeptide, in the hippocampal formation has been shown to reduce epileptic activity and kainate-induced cell death in the hippocampal formation (Haberman et al. (2003) Nature Med. 9:1076-80; Lin et al. (2003) Eur. J. Neurosci. 18:2087-92). Thus, as with AAV-mediated hippocampal NPY expression, epileptic activity was reduced but not abolished.
Increased release of a neurotransmitter often leads to compensatory downregulation of the receptors mediating the effects of the neurotransmitter. Accordingly, overexpression of neuropeptides like NPY, galanin, or somatostatin might lead to downregulation of the corresponding receptors of these neuropeptides. Indeed, in patent PCT WO 2005/037211 A2, a prominent reduction in Y1 receptor binding sites was reported following overexpression of NPY via AAV vectors. Thus a therapeutic effect of overexpressing neuropeptides could taper off with time due to changes in receptors mediating the therapeutic effect. In conclusion, previous studies show that targeted expression of NPY and galanin are not sufficient to abolish seizures. In addition, compensatory downregulation of neuropeptide receptors in response to induced expression of neuropeptides via administration of viral vectors is likely to limit a potential therapeutic effect with time. Based on these considerations, the present invention aims at treating epilepsy and other neuropsychiatric diseases by inducing expression of a combination of one or more neuropeptides (NPY, galanin, somatostatin) and/or one or more of their corresponding receptors (Y1, Y2, Y4, Y5, y6, GALR1, GALR2, GALR3, SST1, SST2, SST3, SST4, SST5) via viral vectors acting in key brain regions.